Sleeves ease fibre joints

Sleeves ease fibre jointsMelanie Reynolds Single mode optical fibres are notoriously difficult to join together, requiring alignment within micrometres. Traditionally, connection is made by terminating the fibres with ferrules which are then held in a stable position by a sleeve. To achieve the dimensional tolerances needed is a costly process requiring the ferrules and sleeves to be made by processing ceramics or metals. However, a team from NTT Opto-electronics Laboratories, which published its results in the IEE’s Electronics Letters, has succeeded in producing sleeves using the thermoset injection moulding process. The sleeves are formed by injection moulding a pipe of thermosetting epoxy resin and then cutting along its axis to form the split. This process has resulted in sleeves with an inner diameter error within ?2?m and an outer diameter variation along the axis of less than 5?m. The inner surface unevenness was less than 0.1?m, which is comparable to a glass or ceramic surface. Using the sleeves with zirconia ferrules to make up connectors, all the connection losses were less than 0.5dB, with an average loss of 0.09dB. The return loss measured was greater than 50dB. The short and long term reliability of the sleeves are now being investigated.

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